Hydraulic lift truck



@VO 113, H E. PAGE HYDRAUL I C LIFT TRUCK Filed July 25, 1945 2 Sheets-$heet l av. 13, 1945. H. E. PAGE HYDRAULIC LIFT TRUCK Filed July 25, 1943 2 Sheets-Sheet 2 Patented Nov. 13, 1945 UNITED srATss s r FFICE 4 Claims.

the trucks of a height to leave as little clearance as possible between the elevator and the work to be lifted. This practice, however, limits the use of such trucks to the lifting of loads elevated to the heights to which the trucks are specially adapted, and other difficulties have been encountered such as unevenness in the floor or obstructions preventing easy movement of the truck into position under the load where the clearance is limited.

It is, therefore, among the principal objects of my invention to provide a hydraulic lift truck which may be made of minimum height such as to provide ample initial clearance between the truck and work to be lifted, to permit easily rolling the truck under the load, and which at the same time embodies means for establishing quick contact of the elevator with the work to be lifted by using a minimum of manual pumping effort.

Another object is to provide a novel and ellicient means for hydraulically operating the lift mechanism.

Another shortcoming of lift trucks has been their lack of braking mechanism to retard their movement along declining runways and the like after being burdened with a load. It is often necessary in moving a load from one point to another to move the lift truck along such declining runways and in such instances the practice has been for the operator to call for manual assistance to maintain control.

It is, therefore, a further object of my invention to provide a hydraulic lift truck incorporating a braking mechanism, and particularly a hydraulic mechanism actuated by the fluid pressure which maintains the load in elevated position, so that the braking pressure is governed in accordance with the load.

Still further advantages are provided by my invention and how those as well as the objects here inabove pointed out are achieved will be best understood from the following explanation of one adaptation of the invention, for which purpose I shall refer to the accompanying drawings, in which:

Fig. 1 is a side elevation, partly in section;

Fig. 2 is a plan view;

Fig. 3 is an enlarged section of the hydraulic unit;

Fig. 4 is a section taken on line t-s of Fig. 3;

Fig. 5 is a section taken on line 5-5 of Fig. 4:

Fig. 6 is an enlarged fragmentary section showing the brake valve unit; and

Fig. 7 is an enlarged elevation taken on line 1-1 of Fig. 2.

With particular reference to the adaptation shown in the drawings, I show a chassis or base having side frame members 5 and cross members 6, 6a.

Cross member to is somewhat U-shaped (Fig. 7) and has joumalled therein a vertical spindle 1 having a bifurcated lower end 8. An axle d is disposed transversely of the lower end 8 and has wheels l0 rotatably mounted thereon. A cap 12 is secured atop spindle l, as by bolt it. the cap presenting bifurcations it between which is pivoted the operating lever to be described. A rear axle 30 is mounted at its ends in side members 5 and carries wheels 32.

The elevator platform has side members 30, an end member M and cross members at, Ma, the platform being pivoted to swing relative to the chassis by means of links 35, 35a, 45b. The lower ends of links 45a are formed integral with a sleeve 64 which is rotatably mounted on axle 30, links Mb being rotatably mounted at their lower ends on the shaft 30. The upper ends of the links lia, Mb are rotatably secured to a spindle M, which spindle is secured at its ends in the platform side frame members iii, spacer sleeves 66 being interposed between the outer ends of links 45a, 4512. It will be observed, therefore, that the elevator is raised from the lowered position shown in Figs. 1 and 2 by means of rotating the sleeve M, the hydraulic mechanism for which will now be described.

The hydraulic unit comprises a body 58 having a cylinder or piston chamber 5i within which a work piston is slidably mounted. Piston 65 has a rod 56 which is pivotally secured by bracket members 57 to the chassis side members 5, so that the piston at all times is held against longitudinal movement relative to the chassis while the body 50 moves longitudinally relative to the piston and chassis.

The outer end of cylinder Si is internally threaded and has threadedly mounted therein a block 60 which presents a longitudinal cylinder bore BI within which a pumping piston 84 is reciprocally mounted. The outer end of block 80 presents bifurcations or extensions whose outer ends are pivotally secured to an arm I0, the lower end of the arm ll being cast integral with the sleeve 44 so that arm 10 in conjunction with the sleeve and links 4511 constitute a bell crank. Thus longitudinal movement of the body 50 causes rotation of the sleeve 44 and consequent A bell crank 90a is pivotally mounted by pin 9I' to a supporting bracket 93, the latter bracket having two arms 93a secured to the side frame members and two arms 98b secured to the cross member 8. One arm of the bell crank is pivotally connected to a link 15a. which in turn is secured at its opposite end to links I5. The other arm of the bell crank has a plane bottom surface to be engaged by the roller 84 of the operating lever so that manipulation of the handle 80 operates the lever and bell crank to cause reciprocation of piston 54. A compression spring 94 interposed between slide bar I3 and the block 60 urges the piston 64 outwardly of cylinder 0|.

A hydraulic fluid reservoir is provided in body 50 and consists of that portion of chamber 5| ahead or to the right of piston 55 and the auxiliary chamber 80, a passageway 9| being provided through the wall separating auxiliary chamber 00 from chamber 5!. A filling plug 83 is threadedly mounted in a hole in the body communicating with the chamber 5|.

Within the forward or left-hand end of the body I provide two transverse bores 95 and 96 (Figs. 3 and 4). Within bore 95 I threadedly mount a valve housing I00 having a longitudinal bore IOI." A transverse passageway I03 and a tube I04 provide communication between bore MI and cylinder BI, and a passageway I06 provides communication between bore IM and chamber portion 5Ia behind piston 55. A poppet valve I I0 seats towards the reservoir or inlet end of bore IOI, being normally maintained in seated position by gravity although spring means may be utilized, if desired, said poppet valve having oppositely disposed stems i I0a, I IIlb. A ball valve H5 in bore IOI seats towards poppet IIO, being normally held against its seat by a coil spring H5. This spring H6 is of a strength sufficient to maintain ball II5 seated against pressure in cylinder I5I during preliminary operation of piston 64 or until the elevator platform contacts the work to be lifted. An inlet chamber I I1 communicates with the reservoir and with the bore IOI through ports II8 provided in the inner end of the valve housing.

With the elevator in the lowered position shown in the drawings, actuation of the handle 80, together with pressure of spring 94, reciprocates piston 54. On each suction stroke poppet H0 is unseated and fluid is drawn from the reservoir into cylinder 5|. Spring IIB being of a strength to maintain ball valve II5 seated until the elevator contacts the load to be lifted, each of the preliminary pressure strokes of piston 54 thus cylinder 6 I moves the body 50 to the left, causing arm I0 to rotate sleeve 44 and swing the links 45a to raise the elevator into contact with the work.'

ence will be made hereinafter to the specific construction of poppet IZI'.

After the elevator contacts the load to be lifted, further movement of the platform is caused by pressure in cylinder IiI generated by continued reciprocation of the pumping piston 64. That is, the contact of the elevator with the loadaffords sufllcient resistance to further movement bf the platform to cause ball valve II5 to be unseated on each pressure stroke of piston 64, each pressure stroke forcing fluid from cylinder 6|,

through tube I04, past ball valve I I5 and through passageway I05 into chamber 5Ia. This operation causes the body 50 to move further to the left relative to the piston 55 and thus causes further lifting movement of the elevator.

When it is desired to lower the elevator, an eccentric cam I30 rotatably mounted in a longitudinal bore I3I in the body is rotated to first contact and press'inwardly the valve stem H011 to unseat poppet H0 and release pressure from Further rotation of the cam causes stem IIOb, which is normally spaced from the ball valve I I5, to move into contact with and unseat ball II5 to release the pressure from cylinder 5|, the elevator then moving into lowered position by virtue of its weight, or its own weight plus the carried weight. A compression spring III is disposed in chamber 5| between piston 55 and plug to return the elevator to lowered position if its weight or load should be insufficient.

The mechanism for operating the cam I30 includes the shaft I33 upon which the cam is secured, which shaft is rotated from a. foot pedal I35a provided by one leg of a bell crank I35, a second bell crank I31, a radial arm 138 secured on shaft I33, and connecting links I39, I40. A coil spring I35 urges the bell crank I35 against the stop I38a carried by frame member 5. Packing rings I4I are provided at opposite ends of the cam.

Referring now more particularly to the poppet valve I2I, it is mounted in the longitudinal bore of housing I22. Valve I2I has a longitudinal bore I50 which communicates with an inner chamber I5I within which chamber an auxiliary P ppet I53 is reciprocally mounted. To provide a seat for the latter poppet, a plug I54 is secured in the inner end of bore I50, as by peening I50a, and this plug has a port I55 against whose inner peripheral portion poppet I H seats, the poppet being urged against its seat by a spring I 56. Port I55 communicates with the chamber I5I through a port I51 in poppet I53 and thus the latter poppet I5I functions as a safety relief valve in the event pressure in cylinder 5| becomes too great.

In the movement of lift trucks from one place to another, particularly while heavily loaded. when any declining runway is traversed, the truck is apt to run away unless some braking or restraining power is applied. I have, therefore, incorporated in my lift truck a hydraulic brake which is actuated from the pressure side of the work piston Bi so that the braking pressure applied is proportioned to the load.

This braking mechanism includes a brake drum idt having an expanding brake band lti which is expanded into braking position by any suitable hydraulic mechanism, such as plungers its actuated by fluid pressure applied through tube lot, there being a spring its normally urging the band contracted.

A valve housing itl is secured to one or the side frame members, this housing having a longitudirisl bore providing a fluid. chamber its in which a piston ilt having two heads iltlo, lid?) is reciprocally mounted. ii pair oi ports ill,

will are provided through the" side wall oi the housing, port i'li communicating with the said tube ltd and port ill communicating with the reservoir in the body til through tube lit. ll.

bell crank lit is pivotally secured on side frame member t and has one of its arms operatively connected to the piston by means of connesting rod lit. The bell crank is operated to actuate the piston by means oi a Bowden wire ill connecting at one end to the bell crank lid and connecting at its other end to a conventional operating lever, not shown, mounted on the hamdle a tube ltd establishes communication between body chamber lilo and the bore oi valve housing till through port ltd. A coil spring secured to trance member ii and crank till urges the crank into the inoperative position shown in the drawings. 7 v

With the parts in the position shown in Fig. 6 the loraire is inoperative, To brake the truelr, the Bowden wire ill is operated to move piston ilt downwardly in its cylinder until piston portion ilta uncovers port 082 and piston portion lldb covers port ilil. Thus the bralreoperating plunger it? is subjected to fluid pressure or. the pressure side of piston lib, which is determined by the load on the elevator. If the iiuid pressure in chamber tic. should be insufllcient, it may be augmented by operating the pumping piston o l to increase the pressure in chamber bio.

While, in the foregoing, I have resorted to considerable detail of structure and association of parts in describing a particular example of my invention, I wish it to be understood that I have done so merely to make my invention understood and that I do not limit my invention to such details. On the contrary, my invention is only to be limited as appears in the appended claims.

I claim:

1. In a. hydraulic lift device having a base and a work-supporting member movably mounted thereon, operating means comprising a body having a bore therein providing a piston chamher and a fluid reservoir, 9. work piston reciprocally mounted in the piston chamber and separating the reservoir from the remainder of said chamber, a plug secured in and closing one end of the bore, a cylinder bore longitudinally in the plug coaxial with the body bore, a pumping piston reciprocally mounted in said cylinder bore and operable independently of the work piston to move the work-supporting member into contact with the work and operable thereafter to exert suillcient pressure in the piston chamber to cause further movement of the work-supportins member.

2. In a hydraulic lift device having a base and a work-supporting member movably mounted thereon, operating means comprising a body movable relative to the base and operatively secured to the work-engaging member, said body presenting a longitudinal bore, a work piston slidably mounted in one end of the bore and separating it into a pressure chamber and a fluid reservoir, 8, rod extending from one end of the body and securing the work piston to the base, a block threadedly mounted in the other end of the bore, said block presenting a cylinder bore coaxial with the body bore, a pumping piston reciprocally mounted in the last-named bore, means providing a fluid passageway between the last-named bore and the pressure chamber, a check valve in said passageway seating towards the said last-named bore, means providing a fluid passageway between the last-named'bore and the reservoir and a check valve in the lastnamed passageway.

In a hydraulic lift truck, the combination of a chassis, a work-supporting platform, a spindle mounted transversely of the chassis, a sleeve rotatably mounted on the spindle, link means secured to the sleeve and to the platform whereby upon rotation oi the sleeve the platform is moved about a radius relative to the chassis, a radial arm secured on the sleeve, a body having a pair of spaced parallel longitudinally slotted extensions pivotally secured to the arm, said body being movable longitudinally relative to the chassis, a pair of longitudinal, oppositely disposed, piston chambers in the body, a work pis ton secured to the base and slidably mounted in the first of the chambers, a pumping piston reciprocally mounted in the second chamber and having a rod disposed between said extensions,

a cross pin extending through the rod and being slidable in said slots, on operating lever pivotally mounted on the base, link means operatively connecting the lever to the cross pin, said body so presenting a fluid reservoir, means providing a fluid passageway between the reservoir and the second chamber, a check valve in the passageway seating towards the reservoir, means providing a second fluid passageway between the first and second chambers, a check valve in the lastnamed passageway seating towards the second chamber, means providing a third fluid passageway between the reservoir and the first chem-- her, and a check valve in the last-named passageway seating towards the reservoir.

4. In a hydraulic lift truck, 'the combination of a chassis, a work-supporting platform, a spinclle mounted transversely of the chassis, a sleeve rotatably mounted on the spindle. link means secured to the sleeve and to the platform whereby upon rotation of the sleeve the platform is moved about a radius relat ve to the chassis, a radial arm secured on the sleeve, 9, body having a pair of spaced parallel longitudinally slotted extensions pivotally secured to the arm, said body being movable longitudinally relative to the chassis, a, pair of longitudinal, oppositely disposed, piston chambers in the body, a work piston secured to the base and slidsbly mounted in the first of the chambers, a pumping piston reciprocally mounted. in the second chamber and having a rod disposed between said extensions, a cross pin extending through the rod and being slidable in said slots, on operating lever pivotally mounted on the base, link means operatively connecting the lever to the cross pin said body presenting a fluid reservoir, means providing a fluid passageway between the reservoir and the second chamber, a check valve in the passageway seating towards the reservoir, means providing a second fluid passageway between the first and second chambers. a check valve in the lastnamed passageway seating towards the second chamber, means providing a third fluid passageway between the reservoir and the first chamber, a check valve'in the last-named passageway seating towards the reservoir, and spring means normally urging the check valve in the second passageway into seated position, said spring means being unyieldable to pressure generated in the second chamber when the work-supporting platform is not burdened with a load to be lifted, and being yieldable to said pressure when said platform is burdened with a load to be lifted. HERBERT E. PAGE. 

